1. Field of the Invention
The present invention relates to wet processes for semiconductor device fabrication using at least one of cathode water and anode water, and also the cathode water and anode water produced by electrolysis, which is used in the wet processes.
2. Description of the Related Art
A variety of wet processes using a large amount of chemicals, such as wet-etching, cleaning and rinsing processes, are performed several times to manufacture a complete semiconductor device. For example, in a particle removal or cleaning process, a xe2x80x9cStandard Cleaning Solution (SC1)xe2x80x9d is widely used, which is a mixture of ammonium hydroxide, hydrogen peroxide, and water. In addition, a sulfuric peroxide mixture (SPM), which is used to remove polymers or organic byproducts resulting from a dry etching process to form a metal interconnect, or contact hole or via, is a mixture of sulfuric acid and hydrogen peroxide.
Unfortunately, these cleaning solutions can damage metal layers exposed to the solutions. Furthermore, since such large amounts of chemicals are used during the manufacture of semiconductor devices, there is a continuing desire to reduce the amount of the chemicals used, to thereby reduce manufacturing costs and comply with environmental and ecological initiatives.
The use of electrolytic ionized water in wet processes associated with the semiconductor device fabrication has been introduced, for example, in U.S. Pat. Nos. 5,824,200 and 5,616,221. As taught in these disclosures, the amount of chemicals used in wet processes can be significantly reduced if the electrolytic ionized water is used together with the chemicals, which ensures environment-friendly wet processes. In particular, U.S. Pat. No. 5,824,200 (""200 patent) produces electrolytic ionized water by directly supplying electrolytes into a cathode cell or anode cell. U.S. Pat. No. 5,616,221 (""221 patent) uses electrolytic cathode or anode water obtained by performing a preliminary electrolysis and further adding another electrolyte.
For the ""200 patent, however, corrosion of the electrolyzer is a problem due to the direct supply of electrolyte into the cathode or anode cell, so that the resulting ionized water contains a large amount of metals or particles. For the ""221 patent, an ammonia electrolyte is added to the effluent cathode water from the cathode cell, whereas a hydrochloric acid electrolyte is added to the effluent anode water from the anode cell. Accordingly, when there is a need to use both the cathode water and anode water for a wet process, the preparation process becomes complicated due to a variety of considerations, and the amount of electrolytes that are used increases.
Therefore, it would be desirable to perform wet processes with an appropriate electrolytic ionized water that can be produced with a small amount of electrolyte through a simple process without generating contaminants.
It is an object of the present invention to provide a wet process used in the fabrication of a semiconductor device, where the wet process uses at least one of anode water containing oxidative substances and cathode water containing reductive substances, wherein the anode water and cathode water are produced with a small amount of electrolyte through a simple process without generating contaminants, and are readily applied to the wet process.
It is another object of the present invention to provide anode water containing oxidative substances, and cathode water containing reductive substances, for use in wet processes for semiconductor device fabrication.
The present invention is achieved by a wet process performed with cathode water and anode water produced by electrolyzing an electrolyte in a 3-cell electrolyzer. The 3-cell electrolyzer includes an anode cell, a cathode cell, and an intermediate cell between the anode and cathode cells, which are partitioned by ion exchange membranes.
It is preferable that an ion exchange membrane between the cathode cell and the intermediate cell includes an anionic exchange membrane adjacent to the intermediate cell and a fluorine-based cationic exchange membrane adjacent to the anode cell. An ion exchange membrane between the cathode cell and the intermediate cell may include a cationic exchange membrane adjacent to the intermediate cell and an anionic exchange membrane adjacent to the cathode cell.
Deionized water is supplied into the anode cell and the cathode cell of the 3-cell electrolyzer and the intermediate cell is filled with an electrolytic aqueous solution to perform electrolysis. At least one of the anode water containing oxidative substances, or the cathode water containing reductive substances, which are produced by the electrolysis, are used in a wet process.
In one embodiment, the electrolytic aqueous solution is a 3-15% by weight ammonium hydroxide solution. In this case, the anode water may have a pH of 7-9, and an oxidation-reduction potential of +100 mV or more, and the cathode water may have a pH of 9 or more, and an oxidation-reduction potential of xe2x88x92500 mV or less.
In another embodiment, the electrolytic aqueous solution is a 3-15% by weight hydrochloric acid solution. In this case, the anode water may have a pH of 4 or less, and an oxidation-reduction potential of +700 mV or more, and the cathode water may have a pH of 3-5, and an oxidation-reduction potential of xe2x88x92100 mV or less.
In still another embodiment, the electrolytic aqueous solution is a mixture of 130% by weight ammonium hydroxide and 1-30% by weight fluoride-containing solution. The fluoride may be a hydrogen fluoride or ammonium fluoride. In this case, the anode water may have a pH of 6 or less, and an oxidation-reduction potential of +300 mV or more.